This invention relates to an improved, cross current, moving bed type adsorption device for use in removing specific components contained in a gas, such as the sulfur oxides contained in an exhaust gas.
In the case where a large volume of gas is treated with a solid adsorbent it is known that the cross current, moving bed type, adsorption device is advantageous in the points of equipment area, controllability of the flow rate of the adsorbent and gas load, said device being constructed so that the gas flow is brought into contact with the adsorbent particle moving bed in a cross current manner. U.S. Pat. No. 3,716,969 issued to Isamu Maeda describes that a continuous moving layer adsorption device employed in an exhaust gas desulfurization system is made of an adsorption vessel as the main body filled with activated carbon and a rectifying device included therein, the adsorption vessel main body comprising a side wall provided with a number of louvers and located at the gas-introducing side of the vessel, another side wall having delivery holes located at the gas-exhausting side of the vessel, the distance between the gas-introducing side wall and the gas-exhausting side wall being larger toward the downward portion of the vessel, a hopper-like portion provided adjacently below the two side walls, and an elongated port provided at the bottom of the hopper-like portion for delivering the activated carbon; and the rectifying device comprising a rectifying body placed in the hopper-like portion and a rectifying plate extended downwardly from the rectifying body. According to this adsorption device, the center-dropping phenomenon and the suspension phenomenon of adsorbent particles can be prevented, said phenomena being apt to take place in the moving bed of the box-type moving bed adsorption device, thereby ensuring the uniform flow down of adsorbent particles. In this connection, the center-dropping phenomenon is defined to be a phenomenon wherein the centrally located portion in the layers of the adsorbent particles just above the discharging port fall down prematurely, and the suspension phenomenon is defined to be a phenomenon wherein the adsorbent particles filled inside of the adsorption vessel is suspended in a crust-like configuration caused by a lateral compressive force, both of which are detailed in U.S. Pat. No. 3,716,969.
However, even such a device involves many troubles in order to achieve the uniform gas distribution. The reason is that in order to increase the gas treating capacity of the device it is inevitably necessary to increase the height of the adsorbent filled layer and consequently there is created a conspicuous difference in layer pressure between the particles located at the upper part and those located at the lower part thereof since the adsorbent filled bed is made to have a divergent structure, whereby the amount of the exhaust gas passing through the upper part is markedly increased. In addition, the increase in the height of the adsorbent particle layer brings about troubles such that the particles located at the bottom of the layer are liable to crush and wear by their own pressure and further attention must be paid to a probability that the uniform flow down of particles is disturbed, although it is caused partly because the width of the bed is increased as a result of employing a large-scale equipment. Accordingly, it is natural that the device of U.S. Pat. No. 3,716,969 as it stands has a limitation in its capacity.